1. Field of Invention
This invention relates to a turbine and rotor therefore with an axis of rotation substantially parallel to a gas/fluid flow. More particularly, this invention relates to an un-enclosed wind/water turbine or a rotor/impellor housed within a duct extracting or converting energy from/to a moving stream of gas or fluid.
2. Background
On the most part, modern wind turbine rotors are of low solidity and have few long straight blades of “airfoil” section revolving around a central horizontal axis with a large proportion of their blade areas situated within the inner half of their diameters.
The very high tip speed ratios involved in obtaining maximum efficiency can greatly add to noisy operating conditions of these turbines.
The present inventor has realized that the outer one third of any turbine rotor does most of the useful work in converting the kinetic energy from a moving gas/fluid flow into available torque as torque is a function of force×radius, and also that it is more beneficial in power production to have an increased gas/fluid flow velocity rather than having an increase in the overall size of the turbine rotor, the present invention seeks to situate the majority of the working surface being presented to the gas/fluid flow in this outer region in an effort to achieve a high mechanical efficiency within a design that remains relatively basic, un-encumbered, free-flowing and is does not rely on high tip speed ratios.
The maximum theoretical percentage of energy that can be extracted from a wind flow is 59.3% (the BETZ limit) and this invention has shown University supervised wind tunnel test results supporting of a maximum co-efficient of power above 52%.